Powerful Downpour Floods Ontario Streets

Flooding from record rain made driving a mess in Ontario. Tony Shin reports for the NBC4 News at 5 p.m. on Tuesday, Sept. 15, 2015. (Published Tuesday, Sept. 15, 2015)

A low-pressure system that began approaching the Southland Monday unleashed its biggest volume of rainfall Tuesday morning, creating traffic and other roadway headaches and causing flooding that threatened at least one home near a construction site.

Morning downpours caused havoc on freeways and streets. The 710 Freeway was closed in both directions in the Bell area due to flooding and an overturned big rig blocked traffic on the 210 Freeway in Pasadena.

In San Gabriel, a deluge of storm runoff flooded a construction site, causing a temporary wall to give way and the backyard of an adjacent home to collapse into the rushing Rubio wash, forcing the
evacuation of the house.

The collapse occurred around 5:30 a.m. in the 5300 block of Pondosa Avenue as a rain storm pounded the region, officials said. When the soil gave way, it left the home teetering precariously above the Rubio wash.

Rainfall Causes Evacuations After Damaging Retaining Wall

A deluge of storm runoff flooded a construction site in San Gabriel, causing a temporary wall to give way and the backyard of an adjacent home to collapse into the rushing Rubio wash, forcing the evacuation of the house. Ted Chen reports for the NBC4 News at 5 p.m. on Tuesday, Sept. 15, 2015.

(Published Tuesday, Sept. 15, 2015)

Officials with the Alameda Corridor-East Construction Authority, which is conducting the construction project behind the home, said the torrent of storm runoff washed away a temporary concrete wall that had been built to control water during the project.

The authority is putting the family up in a hotel while authorities work to secure the property.

The homeowner, Ona Hu, said that when the collapse occurred, she thought it was an earthquake.

Residents of several other nearby homes were also evacuated to ensure no other structures were impacted by the collapse. No injuries were reported.

As of 3 p.m., 2.39 inches of rain had fallen in downtown Los Angeles, shattering the record for this date of 0.03 inches, set in 1968. Rainfall records were also set at UCLA, with 2.12 inches; Los Angeles International Airport, with 1.79 inches; and Burbank Airport, with 1.02 inches, according to
the NWS.

Rainfall records were also set in Lancaster, Palmdale and Sandberg.

According to the NWS, the 2.39 inches of rain in downtown Los Angeles made Tuesday the second-wettest September day since record-keeping began in 1877.

The wettest September day was Sept. 25, 1939, when 3.96 inches of rain fell.

The rain also made September 2015 the third-wettest September in downtown Los Angeles since record-keeping began in 1877. The wettest was in 1939, with 5.67 inches.

The rainfall caused major headaches for morning commuters, with wet conditions triggering traffic mishaps throughout the Greater Los Angeles area, causing street flooding in several places and prompting the issuance of SigAlerts on several freeways, some of which were turned into parking lots.

"We have certainly seen an real increase in crashes on area freeways,'' said CHP Officer Francisco Villalobos. "There's been a lot of spinouts, overturned vehicles, jackknifed trucks and fender benders."

In West Hollywood, a leaking roof prompted the evacuation of at least 135 residents from a three-story assisted-living apartment building at 838 W. Knoll Drive in West Hollywood, according to a Los Angeles County Fire Department dispatcher.

Deputies from the sheriff's West Hollywood station and officials from Metro were called at 5:03 a.m. to assist in the evacuation of the residents and take them by bus to the West Hollywood Park Auditorium at 647 San Vicente Blvd., said Lt. Edward Ramirez of the sheriff's West Hollywood station.

Thousands of Los Angeles Department of Water and Power customers lost power due to the storm, and the rain kept repair crews busy throughout the day.

The weather system's main band of rain hovered over the region until around noon, but scattered showers continued to douse select areas through the afternoon.

There was still about a 20 percent chance of rain Tuesday night, according to the NWS. The storm is expected to be largely out of the area by Wednesday.

Marginally lower temperatures were expected under partly cloudy skies Wednesday, followed by a slight temperature uptick under sunny skies on Thursday and a return to highs in the 90s in some Southland communities on Saturday.